Fuel-based heating systems typically employ a high voltage spark ignition system or igniter to initiate combustion of a fuel-air mix within burners for boilers, forced air furnaces and water heaters. Such burners typically burn fuel oil, diesel oil, or natural gas in both residential and commercial heating applications. For example, a residential oil burner for heating a home may include a burner motor that drives a fan or blower and oil pump to force the fuel-air mix into a burner flame tube or combustion head. The burner also includes a high voltage igniter to create a spark in the flame tube that ignites the fuel-air mixture, a flame sensor to detect when a stable flame is present, and an electronic control module. The electronic control module often controls and monitors all the burner functions, timings, and maintains regulated operation of the system, for example, by further monitoring a user set thermostat.
Despite a convenient modular construction, there is still a considerable number of parts required within such burner systems that require substantial material and labor costs to fabricate and assemble. One such component that requires detailed fabrication costs is the high voltage igniter. The igniter may essentially comprise a high voltage switching power supply that has many electronic components mounted on a printed circuit board (PCB) and also includes, for example, a custom built high voltage (HV) switching transformer. The custom high voltage transformer may be potted, for example, in epoxy, urethane, silicone rubber or another such insulative potting material. The HV transformer and all the components may then be mounted on the PCB and hand or wave-soldered to connect all the components and supply leads to the PCB. High voltage insulators may then be hand soldered, bolted, or otherwise attached to the PCB, for connection to external high voltage terminals of the flame tube. The PCB along with the HV transformer may then be potted, for example, within a protective case or cover housing to electrically insulate and protect the circuit, for example, from the user, the fuels, and mechanical damage. Such material and assembly costs, however, add much to the cost of such systems.
The custom built high voltage transformer, for example, is one particularly expensive component that adds considerable cost to the igniter. Several reasons for this high cost is that the high voltage transformer is often a switching transformer that requires a custom molded bobbin and one or more core pieces, multiple custom wound coils, several high voltage insulator components, hand soldering, and meticulous hand assembly to accommodate the particular demands associated with fabricating a high voltage switching power supply.
For example, some of these assembly cost considerations involve attention to isolation spacing and/or insulation thickness to accommodate high voltage breakdown issues. In addition, to accommodate switching issues, component or wire placement and layout may become important, particularly when higher switching frequencies are utilized. Another assembly cost is the amount of potting material which is used to encase the PCB and HV transformer of the igniter, and the time required for such potting operations, which may need to be done in a partial vacuum to avoid bubbles that lower the breakdown voltage in the respective area. Thus, the overall size of the components of the igniter becomes a cost issue, since more potting material and time may be required to complete the potting operation in a difficult manufacturing environment.
Heating applications likely produce the greatest potential for component failures, where the igniter and the electronic control module may be particularly susceptible to extremes of thermal degradation and chemical changes due to exposure to fuels. Therefore, the enclosures, potting material used, and mounting locations of such assemblies represent important issues for the reliability and safety of a fuel-based burner.
Accordingly, for reliability, cost, and simplicity of assembly reasons, there is a need for an improved igniter for a fuel-based burner that uses smaller and more cost effective components.